Project Summary? Patients who receive the unfortunate diagnosis of triple negative breast cancer (TNBC) have very poor therapeutic options and suffer from a high rate of post-surgery recurrence, metastasis, and mortality due to this devastating disease. Recurrence occurs due chemotherapy-resistant cell survival after drug treatment and surgery. Recurrent TNBCs are lethal, and no molecularly targeted therapies are approved for these patients. Up to 40% of TNBC specimens collected from residual disease after chemotherapy have genomic alterations that cause activation of the phosphatidyl inositol-3 kinase (PI3K) / mechanistic target of rapamycin (mTOR) signaling axis, suggesting the crucial role of this pathway in TNBC chemotherapy resistance and recurrence. Based on published data and our own preliminary data, we are especially interested in therapeutic targeting of the mTOR kinase-containing complex mTORC2, which we believe is a key node in this pathway that drives cell survival and drug resistance in TNBCs. However, there are no existing drugs that selectively inhibit mTORC2, motivating the current proposal which his focused on development of the first highly selective and potent nanomedicine inhibitor of mTORC2 for treating patients with TNBC. Our central biological hypothesis (supported by our rigorous preliminary studies) is that selective mTORC2 inhibition, achieved in a way that spares mTORC1 signaling, will produce superior therapeutic response in TNBCs relative to existing drugs that can inhibit mTORC1 but not mTORC2 or that nonspecifically block both mTORC1 and mTORC2. The overall goal of this collaborative, multi-PI project is to optimize pharmacokinetics of nanoparticle technology for effective delivery of mTORC2-targeting RNAi to TNBC tumors. We specifically propose to test apply next generation nanocarrier surface chemistry and dual carrier/cargo hydrophobization principles to yield an optimized, enabling technology for development of a previously inaccessible mTORC2- selective therapeutic. The proposed project is uniquely accessible through the expertise of the multi-PI interdisciplinary team with bioengineering expertise in polymeric nanotechnologies for intracellular biologic drug delivery (Duvall), BC PI3K/mTOR signaling pathway therapeutics (Cook), and cutting edge preclinical models of BC, including highly clinically-relevant patient derived xenograft (PDX) models (Brantley-Seiders). The group?s interdisciplinary skillset will enable previously-inaccessible mTORC2 investigations and lead to more effective therapies for TNBC patients. This advance will foster unprecedented studies of mTORC2 while providing a novel strategy to treat PI3K/mTOR-driven TNBCs.